1. Field of the Invention
The present invention relates to a tension control device of magnetic tape in a tape running system of a video tape recorder (VTR) or the like.
2. Description of the Prior Art
In the case of an apparatus which draws out a magnetic tape (hereinafter referred to as tape) from a supply reel for recording and reproducing signals, such as in the VTR, it is required to keep constant the tension of the drawn-out tape in order to magnetically record and reproduce signals stably while maintaining a contact state between the tape constant and the magnetic head. Keeping the tape tension constant is also demanded from the viewpoint of decreasing tape damage.
In order to stabilize the tape tension, hitherto, it has been attempted to detect the tension of the drawn-out tape, feed it back, and control the torque of a first motor for directly driving the supply reel on which the tape is wound, thereby stabilizing the tension of the tape (for example, "Collection of Technical Papers of Modern VTR Design Technologies," edited by Japan Industrial Technology Center).
In such conventional constructions, there was a limit in enhancing the response of the feedback system including the first motor to cause the supply reel to follow up the motion of the takeup reel or the capstan responsible for speed control of the tape. In particular, if the response of the capstan or the takeup reel to a tape speed command is increased in order to improve the controllability, the tape becomes too tense or too loose.